Field of the Invention
The present invention relates to a solid-liquid separation device, and more specifically to a solid-liquid separation device such as a filter or filter press of the traveling filter cloth type.
Recently a filter cloth which is made of a textile material with short fibers slanting in one direction piled on its surface or a napped filter cloth with a napped filter layer has been developed (Japanese Patent Publication Nos. SHO 58-207917, 59-115720).
These developments have been followed by a development of filters or filter presses of the so-called traveling filter cloth type (collectively- called solid-liquid separation devices hereinafter) which include a piled filter cloth or a napped filter cloth endlessly moving in one direction on a predetermined path so that a solid-liquid mixture is supplied on the filter cloth and the solid content and the liquid content of the mixture are separated. These solid-liquid separation devices are designed such that a depressurizing suction means is provided on the backside of the filter cloth in opposition to the solid-liquid mixture supply means to suck the liquid content of the solid-liquid mixture supplied on, the filter cloth, thereby promoting the passing of the liquid content and enhancing the efficiency of solid-liquid separation. Such a depressurizing suction means is maintained at such a high vacuum e.g., over 500 mm water column, so that the filter cloth is pulled by the large sucking force.
In the conventional solid-liquid separation device, a depressurizing suction means with a square suction port of constant width is installed in the traveling direction of the filter cloth and a plurality of filter cloth guide rolls of constant length corresponding to the width of the suction port are arranged parallel to one another at the suction port for the purposes of preventing the filter cloth from being deflected by the sucking force. However, the conventional solid-liquid separation device of such a design has the drawbacks mentioned below.
Since filter cloth guide rolls of the constant length are provided to match the shape of the suction port of constant width, every roll end engages with the same area of the filter cloth. Since the suction port is a square of constant width, the side wall of the suction port will linearly abrade the same area of the filter cloth. Thus as a result of being subjected to a large sucking forces and linearly abraded against roll ends and the side wall of the suction port, that area of filter cloth becomes linearly abraded, and in the worst case, becomes torn. The damaged filter cloth will decrease the efficiency of, its solid-liquid separation and will even fail to maintain the depressurized state of the depressing area, whereby its treating ability will be greatly impaired.
It is conceivable to reinforce a particular area of filter cloth with a different material having superior anti-wear characteristics, because it is always one particular area that abrades against the roll ends and the suction port wall. However, passage of the liquid content will be hindered at the reinforced area, thereby decreasing the treating ability of the filter cloth.